Heavy rains have again hit northern Vietnam following the worst floods to hit the region in over 35 years.

At least 82 people have been killed since unseasonal rains started in north-central Vietnam and the capital Hanoi late last month.

Teams using heavy earthmoving equipment are reinforcing a Red River dyke near the city with 12,000 cubic metres of boulders and rocks after more than 800 millimetres of rain pounded Hanoi in five days.

The Red River and its tributaries, burst their banks, inundating rice fields and more than 120,000 buildings, including much of Hanoi.

Many residents complain of receiving little help from emergency workers or soldiers as their neighbourhoods disappeared under a metre of brown floodwater, trapping thousands of people in their houses.

Authorities in the capital say they are trying to contain the spread of dengue fever after 180 cases of the mosquito-borne disease were reported by Hanoi hospitals in a six-day period.